1. Field of the Invention
This invention relates generally to impacting apparatuses which generate impacts required for example to break hard solids or to drive piles into the ground. More particularly, the invention relates to a rotary impacting apparatus.
2. Description of the Prior Art
As is well known, impacting apparatuses have various applications. Chiefly, they can be used to break hardened concrete or asphalt solids at construction sites by using a chisel as a working tool. By selecting suitable working tools, they can also be used to drive piles into grounds or to stamp loose grounds or uncured asphalt pavements.
Conventional impacting apparatuses, particularly solids breakers, can be classified mainly into two types, that is, compressor operated type and engine operated type.
A typical breaker of the compressor operated type comprises a vertically extending cylindrical main body connected to an air compressor through pressure hoses, and a piston reciprocated up and down within the main body by expansion of compressed air supplied to the main body from the compressor. Upon each downward stroke, the piston hits a chisel provided at the lower end of the main body.
With the compressor operated breaker, the piston must be repetitively accelerated and decelerated against its inertial mass, so that it is difficult to achieve a high impacting frequency and to avoid vibration resulting from such reciprocation. Further, because of sliding reciprocation of the piston with resultant heat generation, the cylindrical main body must be made of a tough and heavy material, consequently making large the total weight of the apparatus including the compressor (also heavy). More importantly, the compressor is very high in energy consumption.
On the other hand, a typical breaker of the engine operated type is disclosed for example in UK Patent No. 1,358,674. Specifically, the breaker of this patent comprises a vertically extending cylindrical main body in which a movable cylinder is slidably reciprocated up and down by an engine connected thereto via a crank mechanism. A free piston is slidably guided within the movable cylinder and divides the interior thereof into two pressure chambers. The free piston has an impact rod hermetically projecting downward through an end wall of the movable cylinder. When the movable cylinder is reciprocated, the two pressure chambers are alternately compressed by inertial delay of the free piston to reciprocate the piston upon subsequent expansion of the pressure chambers. On each downward stroke of the piston, the impact rod hits a chisel provided at the lower end of the main body.
The engine operated breaker needs no compressor, so that it is much higher in energy efficiency. However, the use of the movable cylinder and the free piston, which are reciprocating parts, is disadvantageous in view of unacceptable vibration, limitation on achievable impacting frequency, and inevitable weight increase, as described with respect to the compressor operated breaker. Further, the engine operated breaker requires a number of components in a complicated arrangement.
Both types of prior art breakers or impacting apparatuses rely on air compression and expansion as well as on gravity acting on the piston and/or the movable cylinder. Therefore, the prior art impacting apparatus cannot be used in a non-atmospheric or non-gravitational condition, that is, in the space. This is of great disadvantage in view of recent space developments. Moreover, reliance on gravity poses a difficulty in operating the apparatus in a horizontal or upwardly directed posture.